Method for manufacturing cable protection tubes

Abstract

To provide a power communication pipe that is made of a gray hard vinyl chloride resin composition and difficult to deform in a wire common trench.SOLUTION: A power communication pipe 1 is a power communication pipe to be buried underground, and has a straight pipe section 2 with a pipe body 21 made of a gray hard vinyl chloride resin composition including a vinyl chloride resin and a pigment. The pigment includes at least one type selected from a group consisting of non-carbon inorganic pigments and organic pigments, and the infrared reflectance of the inner circumferential surface of the straight pipe section 2 is 20% or more.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a power communication pipe. [Background Art]

[0002] In recent years, for purposes such as landscape improvement and disaster prevention, the undergrounding of electric wires (removal of utility poles), in which power cables and power cable-related facilities are buried underground, has been promoted. When undergrounding electric wires, the power cables are accommodated in cable protection pipes. A plurality of cable protection pipes are connected along the central axis and buried underground to form a cable protection pipeline. As the cable protection pipe, for example, a rigid polyvinyl chloride resin pipe is used.

[0003] The amount of heat generated by a power cable changes in accordance with the amount of current passed, and in summer when power demand increases, the temperature of the power cable becomes extremely high, exposing the cable protection pipe to high temperatures. Therefore, cable protection pipes that accommodate power cables (hereinafter also referred to as "power pipes") are required to withstand earth pressure and wheel pressure at high temperatures, and resins and compounds with high impact strength and heat resistance are used for rigid polyvinyl chloride resin pipes used as power pipes (Patent Document 1). Rigid polyvinyl chloride resin pipes used as power pipes are colored orange.

[0004] When undergrounding electric wires, a common utility tunnel (C.C.BOX) is constructed underground, and a plurality of power cables may be buried in the common utility tunnel. Further, a plurality of communication cables may also be buried in the common utility tunnel. Like power cables, communication cables are also accommodated in cable protection pipes. Since cable protection pipes that accommodate communication cables (hereinafter also referred to as "communication pipes") do not require the same level of impact strength and heat resistance as power pipes, general-purpose rigid polyvinyl chloride resin pipes are used. General-purpose rigid polyvinyl chloride resin pipes are colored gray.

[0005] In a joint utility conduit, as shown in Figure 1, for example, multiple power conduits 120, each composed of multiple power pipes 130 connected together, and one or more communication conduits 220, each composed of multiple communication pipes 230 connected together, are buried underground. One power conduit 120 houses one power cable 110. Multiple communication cables 210 are housed in one communication conduit 220, either directly or inserted into a conduit 240. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Special Publication No. 60-40248 [Overview of the project] [Problems that the invention aims to solve]

[0007] Recently, in order to promote the widespread use of underground utility conduits, it has been approved to use low-cost, general-purpose gray rigid polyvinyl chloride (PVC) resin pipes for power lines instead of the special, high-cost orange rigid PVC resin pipes. Furthermore, regarding communication conduits, instead of constructing curved sections of communication lines using only curved pipes, which are costly to process and install, methods have been developed to construct curved sections of communication lines by connecting straight pipes with special joints, or by connecting straight pipes with sockets and then bending these connection points. However, gray rigid polyvinyl chloride resin pipes generally contain carbon black as a pigment. Because carbon black has high heat retention properties, if gray rigid polyvinyl chloride resin pipes are used as power conduits, they tend to become hot due to the heat generated from power cables. If communication conduits are buried adjacent to power conduits in a joint utility trench, when the power conduits become hot, the heat from the power conduits tends to cause the communication conduits to become hot as well. When gray rigid polyvinyl chloride (PVC) resin pipes are exposed to high temperatures, their strength decreases, and they may deform due to soil pressure and wheel pressure. In particular, if the PVC resin pipes are buried at a shallow depth, the pressure exerted when vehicles pass over them increases, which may cause the pipes to crack or collapse. Furthermore, with regard to communication conduits, if they are warped when installed on curved sections of the conduit, or if warping occurs after installation, the ends of the communication conduits may protrude into the conduit at connection points, potentially damaging the communication cables or conduits inside the conduit.

[0008] The present invention aims to provide a power communication tube made of a gray, rigid polyvinyl chloride resin composition that is resistant to deformation in underground utility conduits. [Means for solving the problem]

[0009] The present invention has the following aspects. [1] Power and communication conduits buried underground, It comprises a straight pipe section with a tube body made of a gray, rigid vinyl chloride resin composition containing vinyl chloride resin and pigment, The aforementioned pigment includes at least one selected from the group consisting of non-carbon inorganic pigments and organic pigments. A power communication tube characterized in that the infrared reflectance of the inner surface of the straight pipe section is 20% or more. [2] The power communication tube according to [1], wherein the pigment substantially does not contain carbon black. [3] The power communication tube according to [1] or [2], wherein the pigment consists solely of non-carbon inorganic pigments. [4] The power communication tube according to [1] or [2], wherein the pigments exhibiting color consist solely of organic pigments. [5] The power communication tube according to [1] or [2], wherein the pigment consists of a mixture of a non-carbon inorganic pigment and an organic pigment. [6] Power and communication conduits buried underground, The device comprises a straight pipe section having a pipe body made of a gray, rigid vinyl chloride resin composition containing a vinyl chloride resin and a pigment, and a coating film located on the inner circumferential surface of the pipe body. The coating film comprises at least one selected from the group consisting of non-carbon inorganic pigments and organic pigments. A power communication tube characterized in that the infrared reflectance of the inner surface of the straight pipe section is 20% or more. (7) The power communication pipe according to (6), wherein the coating film contains substantially no carbon black. Effects of the Invention

[0010] According to the present invention, it is possible to provide a power communication pipe that is formed of a gray rigid vinyl chloride-based resin composition and is less likely to deform in a common utility tunnel. Brief Description of the Drawings

[0011] [Figure 1] It is a partially broken perspective view illustrating a common utility tunnel. [Figure 2] It is a partially broken side view of the power communication pipe according to one embodiment. [Figure 3] It is a partially broken side view showing another example of the power communication pipe. [Figure 4] It is a partially broken side view showing another example of the power communication pipe. [Figure 5] It is a graph showing measurement results of spectral reflectance of inner peripheral surfaces of the power communication pipes of Examples 1, 3 and Comparative Example 1. Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the power communication pipe of the present invention will be described with reference to drawings. However, the present invention is not limited to the following embodiments. In the present invention, "power communication pipe" is a general term for power pipes and communication pipes. "Power pipe" accommodates power cables buried underground. "Communication pipe" accommodates communication cables buried underground together with power cables.

[0013] As shown in Figure 2, the power communication pipe 1 according to one embodiment of the present invention includes a straight pipe section 2 and a socket section 3. The straight pipe section 2 is formed in a cylindrical shape having a uniform diameter. The socket section 3 is formed with an increased diameter at one end side of the straight pipe section 2. The straight pipe section 2 and the socket section 3 are connected by a tapered pipe section 4. The other end of the straight pipe section 2 serves as an insertion section 5 to be inserted into the socket section 3 of another power and communication pipe 1. An insertion marked line 6 for defining the insertion depth into the socket section 3 of another power and communication pipe 1 is provided on the outer circumferential surface of the straight pipe section 2. In the socket section 3, a diameter-enlarged portion 3a for accommodating a rubber ring 11 serving as a water blocking material is formed on the inner circumferential surface of the socket section 3 over the entire circumference.

[0014] The straight pipe section 2 includes a pipe body 21 made of a gray rigid polyvinyl chloride resin composition. The gray rigid polyvinyl chloride resin composition contains a vinyl chloride resin and a pigment. The gray rigid polyvinyl chloride resin composition will be described in detail later. The pipe body 21 may be of a single-layer structure or a multi-layer structure. In the case of a multi-layer structure, the gray rigid polyvinyl chloride resin compositions constituting each layer may be the same or different.

[0015] The nominal diameter of the pipe body 21 may be, for example, 100 to 150 (the outer diameter of the pipe body 21 is 114 mm to 170 mm). When the power and communication pipe 1 is a power pipe, the nominal diameter of the pipe body 21 is typically 100 to 150 (the outer diameter of the pipe body 21 is 114 mm to 170 mm). When the power and communication pipe 1 is a communication pipe, the nominal diameter of the pipe body 21 is typically 100 to 150 (the outer diameter of the pipe body 21 is 114 mm to 170 mm). The nominal diameter is an A designation. The pipe body 21 may be, for example, a VP pipe or a VU pipe specified in JIS K 6741. The VP pipe and the VU pipe have the same outer diameter but different wall thicknesses, and the VP pipe has a greater wall thickness than the VU pipe. Specifically, the value obtained by dividing the outer diameter by the wall thickness (outer diameter / wall thickness) is 17 to 20 for a VP pipe, while it is 30 to 38 for a VU pipe. When the nominal diameters are the same, a VU pipe with a thinner wall thickness is more susceptible to the influence of heat generated from a power cable. In the present embodiment, since the influence of heat generated from the power cable can be suppressed, even when the pipe body 21 is a VU pipe, the extrusion speed during extrusion molding is high, it is less susceptible to the influence of heat, and yellowing (burning) caused by deterioration of the resin itself is less likely to occur. On the other hand, the pipe thickness may be made thicker than that of a VP pipe or VU pipe. For example, the value obtained by dividing the outer diameter by the pipe thickness (outer diameter / pipe thickness) may be set to 15 to 17. By increasing the pipe thickness, the strength can be increased not only at high temperatures but also at low temperatures.

[0016] When the power communication tube 1 is a power tube, the infrared reflectance of the inner surface of the straight tube section 2 is 20% or more, preferably 25% or more, and more preferably 30% or more. If the infrared reflectance is 20% or more, the temperature of the power tube will not rise easily when exposed to heat generated from the power cable, and it will be less affected by heat. A higher infrared reflectance of the inner surface of the straight tube section is preferable, and there is no particular upper limit, but it may be, for example, 60%. If the power communication tube 1 is a power tube, there are no particular restrictions on the infrared reflectivity of the outer surface of the straight tube section.

[0017] When the power communication tube 1 is a communication tube, the infrared reflectance of the outer surface of the straight tube section 2 is 20% or more, preferably 25% or more, and more preferably 30% or more. If the infrared reflectance is 20% or more, the temperature of the communication tube will not rise easily when exposed to heat generated from the power cable, and it will be less affected by heat. A higher infrared reflectance of the outer surface of the straight tube section is preferable, and there is no particular upper limit, but it may be, for example, 60%. If the power communication tube 1 is a communication tube, there are no particular restrictions on the infrared reflectivity of the inner surface of the straight section.

[0018] In this embodiment, the inner surface of the straight pipe section 2 is the inner surface of the pipe body 21, and the infrared reflectance of the inner surface of the straight pipe section 2 can be adjusted by the pigment of the rigid polyvinyl chloride resin composition constituting the pipe body 21 (if the pipe body 21 is multilayered, the pigment of the rigid polyvinyl chloride resin composition constituting the innermost layer). The higher the content of pigment (I), described later, or the lower the content of carbon black in the pigment, the higher the infrared reflectance of the inner surface of the pipe body 21 tends to be. Furthermore, in this embodiment, the outer surface of the straight pipe section 2 is the outer surface of the pipe body 21, and the infrared reflectance of the outer surface of the straight pipe section 2 can be adjusted by the pigment of the rigid polyvinyl chloride resin composition constituting the pipe body 21 (or, if the pipe body 21 is multilayered, the pigment of the rigid polyvinyl chloride resin composition constituting the outermost layer). Infrared reflectance refers to the average value of spectral reflectance at wavelengths of 800 to 1600 nm, and it is particularly preferable that the average value of spectral reflectance at wavelengths of 800 to 1100 nm is 20% or higher. Infrared reflectance is measured using an ultraviolet-visible-near-infrared spectrophotometer. Further details are described in the examples.

[0019] (Gray rigid polyvinyl chloride resin composition) The gray rigid vinyl chloride resin composition (hereinafter also referred to as "this resin composition") contains a vinyl chloride resin and a pigment. This resin composition may contain additives as needed, as long as they do not impair the effects of the present invention.

[0020] <Vinyl chloride resin> Examples of vinyl chloride resins include vinyl chloride homopolymers, vinyl chloride copolymers, and their chlorinated derivatives. These may be used individually or in combination of two or more types. Examples of vinyl chloride copolymers include copolymers of vinyl chloride monomer and monomers or polymers copolymerizable with vinyl chloride monomer.

[0021] Examples of monomers copolymerizable with vinyl chloride monomers include α-olefin compounds such as ethylene, propylene, and butylene; vinyl ester compounds such as vinyl propionate; vinyl ether compounds such as ethyl vinyl ether and butyl vinyl ether; (meth)acrylate compounds such as methyl (meth)acrylate, butyl (meth)acrylate, and hydroxyethyl (meth)acrylate; aromatic vinyl compounds such as styrene and α-methylstyrene; and N-substituted maleimide compounds such as N-phenylmaleimide and N-cyclohexylmaleimide. These copolymerizable monomers may be used individually or in combination of two or more types. Examples of polymers copolymerizable with vinyl chloride monomer include acrylic copolymers composed of alkyl (meth)acrylate monomers, etc. These copolymerizable polymers may be used individually or in combination of two or more types. (Meth)acrylate refers to acrylate or methacrylate. In a copolymer of vinyl chloride, the ratio of vinyl chloride monomer to the above-mentioned copolymerizable monomer or polymer can be appropriately determined according to the performance and purpose of the rigid vinyl chloride resin pipe, and is not particularly limited.

[0022] As the vinyl chloride resin, commercially available products may be used, or those produced by known manufacturing methods may be used. In the production of a homopolymer or copolymer of vinyl chloride, conventionally known methods may be used as the polymerization method for vinyl chloride, etc., such as suspension polymerization.

[0023] The average degree of polymerization of the vinyl chloride resin is preferably 600 to 3000, more preferably 800 to 2000, and even more preferably 900 to 1200. If the average degree of polymerization is 600 or higher, the mechanical strength of the tube 21 is superior. If the average degree of polymerization is 3000 or lower, it is easier to mold. In particular, since power communication tubes are exposed to heat generated from power cables, setting the average degree of polymerization to 900 or higher makes it possible to achieve excellent mechanical strength at high temperatures. In addition, power communication tubes generally have a large outer diameter and are difficult to mix with vinyl chloride resin and pigment, but by setting the average degree of polymerization to 1200 or lower, the fluidity of the vinyl chloride resin is improved, making it easier to mix with the vinyl chloride resin and pigment, and reducing the likelihood of color unevenness. The average degree of polymerization mentioned above refers to the average degree of polymerization measured in accordance with the "Test Method for Vinyl Chloride Resins" of the Japanese Industrial Standard JIS K 6721, using a resin obtained by dissolving a vinyl chloride resin in tetrahydrofuran (THF), removing insoluble components by filtration, and then drying and removing the THF from the filtrate as a sample.

[0024] <Pigments> In this resin composition, the pigment is used to give the resin composition a gray color, as specified in JIS K 6741. The pigments include colored (non-white) pigments to give the resin composition a gray hue. Typically, the pigments include both colored and white pigments.

[0025] The pigment includes at least one selected from the group consisting of non-carbon inorganic pigments and organic pigments (hereinafter, these are collectively referred to as "pigment (I)"). Pigment (I) has lower infrared absorption than carbon black. Therefore, by including pigment (I), the infrared reflectance of the inner surface of the tube body 21 can be increased. The pigment may include other pigments besides pigment (I) as needed.

[0026] Non-carbon inorganic pigments are compounds (oxides, etc.) obtained by chemical reactions of minerals and metals. Examples of non-carbon inorganic pigments include colored (non-white) non-carbon inorganic pigments and white non-carbon inorganic pigments. These non-carbon inorganic pigments can be appropriately combined with the resin composition within a range that allows for color tuning to a gray tone.

[0027] Examples of colored non-carbon inorganic pigments include compounds containing one (single salt) or multiple (double salt) metals selected from the group consisting of chromium, iron, cobalt, copper, manganese, magnesium, bismuth, yttrium, aluminum, and vanadium. Specific examples of double salts include salts of the Fe-Co-Cr system, Cu-Cr system, Fe-Cr system, Fe-Mn system, Cu-Mn system, Cu-Mg system, Cu-Bi system, Mn-Bi system, Y-Mn system, Co-Al system, and Fe-Co-Al-Mg system. Compounds containing the above-mentioned metals include oxides, hydroxides, sulfides, silicates, and ferrocyanides of the above-mentioned metals. These compounds may be used individually or in combination of two or more types. As a non-carbon inorganic pigment that exhibits color, chromium-containing compounds are preferred, and Fe-Cr compounds are more preferred, because they can lower infrared reflectivity. As a non-carbon inorganic pigment that exhibits color, oxides are preferred because they offer superior color stability.

[0028] Examples of non-carbon inorganic pigments that exhibit a white color include metal oxides such as titanium dioxide, aluminum oxide, and zinc oxide. Among these, titanium dioxide is preferred due to its high refractive index and high whiteness.

[0029] When pigment (I) is a non-carbon inorganic pigment, a mixed pigment of a colored non-carbon inorganic pigment and a white non-carbon inorganic pigment is preferred as the non-carbon inorganic pigment, from the viewpoint of coloring the resin composition to gray. In the aforementioned mixed pigment, a black pigment is preferred as the non-carbon inorganic pigment exhibiting color, which is obtained by combining one or more of the above-mentioned non-carbon inorganic pigments exhibiting color. Examples of pigments that exhibit black color include mixed pigments of two or more pigments that exhibit complementary or near-complementary colors; double salt pigments containing multiple metal ions that constitute each of two or more pigments that exhibit complementary or near-complementary colors; and mixtures thereof. From the viewpoint of obtaining higher infrared reflectivity and better color stability, preferred non-carbon inorganic pigments that exhibit color include mixed pigments colored black by combining green chromium oxide (Cr2O3) with its complementary red pigment (e.g., iron oxide); composite oxides containing chromium oxide and iron oxide; or mixtures thereof, with composite oxides containing chromium oxide and iron oxide being more preferred. In the aforementioned mixed pigment, the ratio of the colored non-carbon inorganic pigment to the total content of the colored non-carbon inorganic pigment and the white non-carbon inorganic pigment can be appropriately adjusted within the range in which the resin composition becomes gray, and is not particularly limited, but may be, for example, 18 to 58% by mass.

[0030] Organic pigments are synthesized from petroleum and other sources. Examples of organic pigments include those that exhibit color (non-white) properties. The organic pigments that exhibit color are not particularly limited and include, for example, azo pigments, phthalocyanine pigments (such as copper phthalocyanine), vene pigments, and dye lake pigments. These may be used individually or in combination of two or more. As for organic pigments that exhibit color, phthalocyanine-based pigments are preferred, and phthalocyanine copper is more preferred, due to their superior color stability.

[0031] Pigment (I) may be a colored (non-white) pigment, a white pigment, or a mixture of a colored pigment and a white pigment. Among the pigments (I), non-carbon inorganic pigments that exhibit a white color are preferred. The pigment (I) that exhibits color may be a non-carbon inorganic pigment that exhibits color, a colored organic pigment, or a mixture of a non-carbon inorganic pigment that exhibits color and a colored organic pigment.

[0032] When pigment (I) is a non-carbon inorganic pigment, the content of the non-carbon inorganic pigment is preferably 0.050 parts by mass or more per 100 parts by mass of vinyl chloride resin, from the viewpoint of suppressing unevenness of color tone due to uneven dispersion of the pigment. Furthermore, from the viewpoint of suppressing contamination of equipment during extrusion molding, the content of the non-carbon inorganic pigment is more preferably 0.050 to 0.500 parts by mass per 100 parts by mass of vinyl chloride resin. From the viewpoint of obtaining these effects more favorably, the content of the non-carbon inorganic pigment is preferably 0.055 to 0.450 parts by mass, more preferably 0.065 to 0.350 parts by mass, and even more preferably 0.070 to 0.250 parts by mass.

[0033] When pigment (I) is an organic pigment, the content of the organic pigment is preferably 0.01 parts by mass or more per 100 parts by mass of vinyl chloride resin, from the viewpoint of providing infrared reflectivity. Furthermore, from the viewpoint of providing even more sufficient infrared reflectivity, the content of the organic pigment is more preferably 0.01 to 1.0 parts by mass per 100 parts by mass of vinyl chloride resin. From the viewpoint of obtaining these effects more favorably, the content of the organic pigment is preferably 0.02 to 0.8 parts by mass, more preferably 0.02 to 0.6 parts by mass, and even more preferably 0.02 to 0.4 parts by mass.

[0034] When pigment (I) is a mixture of non-carbon inorganic pigment and organic pigment, the total content of the non-carbon inorganic pigment and organic pigment is preferably 0.01 parts by mass or more per 100 parts by mass of vinyl chloride resin, from the viewpoint of providing infrared reflectivity. Furthermore, from the viewpoint of providing even more sufficient infrared reflectivity, the total content of the non-carbon inorganic pigment and organic pigment is more preferably 0.01 to 1.0 parts by mass per 100 parts by mass of vinyl chloride resin. From the viewpoint of obtaining these effects more favorably, the total content of the non-carbon inorganic pigment and organic pigment is preferably 0.02 to 0.8 parts by mass, more preferably 0.02 to 0.6 parts by mass, and even more preferably 0.02 to 0.4 parts by mass. The ratio of non-carbon inorganic pigments to the total content of non-carbon inorganic pigments and organic pigments is preferably 10 to 100% by mass, more preferably 50 to 99% by mass, and even more preferably 70 to 98% by mass.

[0035] Other pigments include, for example, carbon black. In this resin composition, it is preferable that the pigment substantially does not contain carbon black. Since carbon black has high infrared absorption properties, the fact that the pigment substantially does not contain carbon black makes it easier to achieve an infrared reflectance of 20% or more on the inner surface of the tube 21. "Essentially not included" means that the infrared reflectance does not fall below 20%. The carbon black content is preferably 0.1 parts by mass or less, more preferably 0.01 parts by mass or less, and particularly preferably 0 parts by mass, per 100 parts by mass of vinyl chloride resin.

[0036] The ratio of pigment (I) to the total pigment content in this resin composition is preferably 60% by mass or more, more preferably 80% by mass or more, and particularly preferably 100% by mass. In other words, it is particularly preferable that the pigment in this resin composition consists only of pigment (I).

[0037] The ratio of colored pigments to the total pigment content is preferably 10 to 60% by mass, and more preferably 15 to 50% by mass. The ratio of white pigment to the total pigment content is preferably 40-90% by mass, and more preferably 50-85% by mass.

[0038] In a preferred embodiment of the present invention, the pigment of the resin composition consists solely of non-carbon inorganic pigments. Since non-carbon inorganic pigments have excellent color stability, if the pigment consists solely of non-carbon inorganic pigments, discoloration of the tube body 21 is less likely to occur.

[0039] In another preferred embodiment of the present invention, the pigments exhibiting color in the resin composition consist solely of organic pigments. Since organic pigments have excellent dispersibility in vinyl chloride resins, if the pigments exhibiting color consist solely of organic pigments, color unevenness of the tube body 21 is less likely to occur. In this embodiment, if the pigment includes a white pigment, it is preferable that the white pigment consists only of a white non-carbon pigment.

[0040] In another preferred embodiment of the present invention, the pigment of the resin composition consists of a mixture of a non-carbon inorganic pigment and an organic pigment. If the pigment consists of a mixture of a non-carbon inorganic pigment and an organic pigment, color unevenness of the tube body 21 is less likely to occur, and fading of the tube body 21 can be suppressed.

[0041] When pigment (I) is a mixture of a non-carbon inorganic pigment and an organic pigment, it is preferable that the organic pigment is blue and the other colors are non-carbon inorganic pigments. The blue organic pigment has excellent dispersibility because it is an organic pigment, and also has superior color stability compared to organic pigments of other colors. Therefore, it is possible to suppress color unevenness of the tube 21 while further suppressing fading of the tube 21. Examples of blue organic pigments include phthalocyanine copper (phthalocyanine blue). Other non-carbon inorganic pigments of different colors that can be combined with blue organic pigments include, for example, the aforementioned mixed pigments of a colored non-carbon inorganic pigment (particularly a black pigment) and a white non-carbon inorganic pigment. Combining this mixed pigment with the blue organic pigment further suppresses color unevenness and improves color stability.

[0042] <Additives> Examples of additives include dispersants, stabilizers, stabilizing aids, lubricants, processing aids, antioxidants, and fillers. These additives may be used individually or in combination of two or more types. Among these additives, dispersants, stabilizers, and fillers are preferred. The dispersant is not particularly limited and examples include silica, sodium or ammonium salts of polycarboxylic acids (e.g., polyacrylic acid), and surfactants. These may be used alone or in combination of two or more.

[0043] The stabilizers are not particularly limited and include, for example, organotin stabilizers such as dimethyltin mercapto, dibutyltin mercapto, dioctyltin mercapto, dibutyltin maleate, dibutyltin maleate polymer, dioctyltin maleate, dioctyltin maleate polymer, dibutyltin laurate, and dibutyltin laurate polymer; lead-based stabilizers such as lead stearate, dibasic lead phosphite, and tribasic lead sulfate; calcium-zinc stabilizers, barium-zinc stabilizers, and barium-cadmium stabilizers; stearate-based stabilizers (metal soaps) such as calcium stearate, zinc stearate, barium stearate, and lead stearate; ultraviolet absorbers such as salicylic acid esters, benzofenones, benzotriazoles, and cyanoacrylates; and hindered amine light stabilizers. These may be used alone or in combination of two or more. Among these stabilizers, stearates (stearic acid-based stabilizers) are preferred, and lead stearate is more preferred.

[0044] When stearate is included in this resin composition, from the viewpoint of obtaining even better color stability, the stearate content is preferably 0.5 to 2 parts by mass, more preferably 0.8 to 1.7 parts by mass, even more preferably 1 to 1.5 parts by mass, and particularly preferably 1.1 to 1.4 parts by mass per 100 parts by mass of vinyl chloride resin. When the resin composition contains a non-carbon inorganic pigment that exhibits color, the stearate content is preferably 10 to 54 parts by mass, more preferably 15 to 53 parts by mass, even more preferably 20 to 52 parts by mass, and particularly preferably 22 to 52 parts by mass, per 1 part by mass of the non-carbon inorganic pigment that exhibits color.

[0045] The stabilizing agent is not particularly limited and examples include epoxidized soybean oil, epoxidized linseed oil, epoxidized tetrahydrophthalate, epoxidized polybutadiene, and phosphate esters. These may be used individually or in combination of two or more.

[0046] Lubricants include internal lubricants and external lubricants. Internal lubricants are used to reduce the flow viscosity of the molten resin during molding and to prevent frictional heat generation. The internal lubricant is not particularly limited and examples include butyl stearate, lauryl alcohol, stearyl stearate, epoxidized soybean oil, glycerin monostearate, stearic acid, and bisamide. These may be used individually or in combination of two or more. External lubricants are used to improve the sliding effect between the molten resin and the metal surface during molding. External lubricants are not particularly limited and include, for example, montanic acid wax, paraffin wax, polyolefin wax, and ester wax. These may be used individually or in combination of two or more.

[0047] The processing aid is not particularly limited, and examples include acrylic processing aids that are alkyl acrylate-alkyl methacrylate copolymers with a weight-average molecular weight of 100,000 to 2,000,000. Specific examples include n-butyl acrylate-methyl methacrylate copolymers and 2-ethylhexyl acrylate-methyl methacrylate-butyl methacrylate copolymers. These may be used alone or in combination of two or more.

[0048] The antioxidant is not particularly limited and examples include phenolic antioxidants. These may be used alone or in combination of two or more.

[0049] The fillers are not particularly limited and include, for example, calcium carbonate and talc. These may be used individually or in combination of two or more. Among these fillers, calcium carbonate is preferred from the viewpoint of obtaining better color stability.

[0050] When calcium carbonate is included in this resin composition, from the viewpoint of obtaining even better color stability, the calcium carbonate content is preferably 5 parts by mass or more per 100 parts by mass of vinyl chloride resin. There is no particular upper limit to the calcium carbonate content, but it is preferably 10 parts by mass or less, more preferably 9 parts by mass or less, and even more preferably 8 parts by mass or less per 100 parts by mass of vinyl chloride resin.

[0051] <Manufacturing method for power communication tubes> The power communication tube 1 can be manufactured by a manufacturing method that includes, for example, a step of preparing the resin composition by mixing a vinyl chloride resin, a pigment containing pigment (I), and additives as needed (preparation step), and a step of molding the resin composition (molding step).

[0052] In the preparation process, known methods such as the hot blending method or the cold blending method can be used to mix vinyl chloride resin, pigments, etc. In the molding process, known molding methods can be used for molding the resin composition. For example, a power communication tube 1 can be manufactured by molding the resin composition by extrusion molding to obtain a cylindrical tube with the same diameter, and then expanding the diameter of one end of the tube by methods such as immersing it in a heated oil bath and then inserting an expanding die to form a socket.

[0053] <Application> The power and communication conduit 1 houses power cables buried underground or communication cables buried underground together with power cables. When burying power cables or communication cables underground, typically, multiple power and communication conduits 1 are buried in a manner in which many are connected along a central axis, thereby forming a power conduit or communication conduit.

[0054] The power communication conduit 1 is suitably used in a joint utility conduit. In a joint utility conduit, as shown in Figure 1, for example, multiple power conduits 120, each composed of multiple power pipes 130 connected together, and one or more communication conduits 220, each composed of multiple communication pipes 230 connected together, are buried underground. One power conduit 120 houses one power cable 110. One communication conduit 220 houses multiple communication cables 210, either directly or inserted into a conduit 240. Power and communication pipes 1 can be applied to these power pipes 130, communication pipes 230, etc.

[0055] Although the present invention has been described above with reference to embodiments, the present invention is not limited to the above embodiments. The configurations and combinations thereof in the above embodiments are examples, and additions, omissions, substitutions, and other modifications are possible without departing from the spirit of the present invention.

[0056] The shape of the power communication tube is not limited to that shown in Figure 2. For example, the shape of the receiving portion may differ. For instance, in the above embodiment, an example was shown in which the receiving portion 3 other than the enlarged portion 3a is formed with the same diameter, but as shown in Figure 3, the shape may be such that the diameter decreases from the tapered pipe portion 4 to the enlarged portion 3a. The enlarged diameter portion 3a and the opening of the socket portion 3 may be enlarged so that the straight pipe portion of another power communication pipe inserted into the socket portion can move at a predetermined angle. In this case, a conduit with a curved section can be constructed using a power communication pipe that consists only of a straight pipe portion 2 and a socket portion 3. Power and communication pipes do not necessarily have sockets. In this case, as shown in Figure 4, power and communication pipes 1A and 1B, each having only straight pipe sections 2A and 2B, can be connected to each other using a double socket joint 7, which has sockets at both ends that allow the straight pipe sections 2A and 2B to move at a predetermined angle. This allows for the construction of a pipeline with curved sections using power and communication pipes with only straight pipe sections 2A and 2B and a double socket joint. Thus, when constructing a pipeline with curved sections using power and communication pipes that consist only of straight pipe sections via sockets or joints, the ends of the straight pipe sections protrude into the inner surface of the pipeline at the connection points between the straight pipe sections. However, in the present invention, since the power and communication pipes are less prone to deformation, it is possible to prevent the ends of the straight pipe sections from protruding into the inner surface of the pipeline in unintended directions or dimensions.

[0057] The straight pipe section may have a coating located on the inner surface of the pipe body in addition to the pipe body itself. When a coating is applied to the inner surface of a pipe, the inner surface of the straight section is the surface of the coating. Therefore, if a power communication pipe is a power pipe, the infrared reflectance of the coating surface is 20% or more. When a coating is provided on the inner surface of the pipe, the infrared reflectance of the inner surface of the pipe may be 20% or more, or it may be less than 20%.

[0058] The straight pipe section may have a coating located on the outer surface of the pipe body in addition to the pipe body itself. When a coating is applied to the outer surface of a tube, the outer surface of a straight tube is the surface of the coating. Therefore, if a power communication tube is a communication tube, the infrared reflectance of the coating surface is 20% or more. When a coating is provided on the outer surface of the pipe, the infrared reflectance of the outer surface of the pipe may be 20% or more, or it may be less than 20%.

[0059] When the infrared reflectance of the surface of the coating film is to be 20% or more, it is preferable that the coating film contains pigment (I). The coating film may contain other pigments. From the viewpoint of reducing infrared reflectivity, it is preferable that the coating film is substantially free of carbon black. The coating typically contains a binder in addition to the pigment. Examples of binders include urethane resins, acrylic resins, silicone resins, and fluoropolymer resins.

[0060] The coating can be formed by applying a paint containing pigment (I) to the inner or outer surface of the pipe. Any known coating method can be used, and there are no particular restrictions. The thickness of the coating film may be, for example, 1 to 100 μm. [Examples]

[0061] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited in any way by these examples. Examples 3 and 4 are for reference only.

[0062] (Examples 1-3, Comparative Example 1) <Preparation of rigid polyvinyl chloride resin composition> A pigment composition was prepared by mixing pigments and dispersants according to the formulations shown in Table 1. The obtained pigment composition, vinyl chloride resin, and additives were then mixed by cold blending in a super mixer (100L, manufactured by Kawata Co., Ltd.) to obtain a rigid vinyl chloride resin composition. In the values ​​shown in Table 1, for example, the notation "0.038-0.053" for titanium dioxide means that titanium dioxide was blended in an amount between 0.038 parts by mass and 0.053 parts by mass. Details of each component are as follows.

[0063] • Vinyl chloride resin: Vinyl chloride homopolymer (product name "TS-1000R", manufactured by Tokuyama Sekisui Kogyo Co., Ltd., average degree of polymerization 1000). • Lead stearate: Product name "SAK-NSBN", manufactured by Sunace Co., Ltd. • Calcium carbonate: Product name "Whiteon 305S", manufactured by Shiraishi Calcium Co., Ltd. Titanium dioxide: White inorganic pigment, product name "R-3L", manufactured by Sakai Chemical Co., Ltd. • Chromium compounds: A complex oxide of chromium oxide and iron oxide, a black inorganic pigment. • Cobalt blue: A blue inorganic pigment. • Copper phthalocyanine: A blue organic pigment. • Diketopyrrolopyrrole: Red organic pigment. • Monoazo yellow: A yellow organic pigment. • Carbon Black: Product name "Toka Black #7350", manufactured by Tokai Carbon Co., Ltd. • Dispersant: Silica.

[0064] <Manufacturing of power and communication pipes> The rigid polyvinyl chloride resin composition obtained above was supplied to a twin-screw anomalous-direction rotary extruder (product name "SLM-50", manufactured by Nagata Seisakusho Co., Ltd.) to form a pipe with a nominal diameter of 100 mm, an outer diameter of 114 mm, a length of 1 m, and a pipe thickness of 7.1 mm. The following measurements and tests were performed on the obtained tubes (power communication tubes).

[0065] <Infrared reflectance measurement> Using a UV-Vis-Near-Infrared spectrophotometer (Shimadzu "UV-3600Plus"), the spectral reflectance of the inner surface of the power communication tubes in Examples 1 and 3 and Comparative Example 1 at wavelengths of 800 to 1100 nm was measured, and the average value was taken as the infrared reflectance of the inner surface of the power communication tube. The results are shown in Table 1. The spectral reflectance curves for each example are shown in Figure 4. Note that the infrared reflectance of the inner surface and the infrared reflectance of the outer surface of the power communication tubes fabricated in this example are the same.

[0066] <Compression strength test> A tubular test specimen was prepared by cutting a 50mm length from a power communication tube. To ensure that infrared radiation was uniformly irradiated onto the inner surface of the test specimen, a 250W infrared lamp ("Eye R-type infrared bulb" 250W model, manufactured by Iwasaki Electric Co., Ltd.) was positioned with its irradiation head 40 cm away from the inner surface of the test specimen and facing it. The test specimen was rotated while the infrared radiation was irradiated onto its inner surface for 30 minutes. Immediately after irradiation was completed, a compressive strength test was performed in accordance with the procedure described below, in accordance with the "CCBOX Conduit System Research Association Standard 'Union Conduit for Electric Power Conduits' CCB E003-1:2018". Immediately after irradiation, the test specimen was sandwiched between two flat plates and compressed at a speed of 10 mm / min perpendicular to the pipe axis. The amount of flattening of the test specimen when the specified load was applied was measured, and the flattening ratio relative to the inner diameter was calculated. The load was set to 145 N, which is the specified load for a nominal diameter of 100. The results are shown in Table 1.

[0067] <Impact Resistance Test> A 30cm length was cut from a power communication tube to create a tubular test specimen. The irradiation head of a 250W infrared lamp ("Eye R-type infrared bulb" 250W model, manufactured by Iwasaki Electric Co., Ltd.) was placed 40 cm away from the inner surface of the test specimen and facing it, and infrared light was irradiated for 30 minutes. Immediately after irradiation was completed, an impact resistance test was conducted in accordance with the impact resistance test specified in the CCBOX Conduit System Research Association standard "Union Conduit for Electric Power Conduits, Power Conduit Material" CCB E003-1:2018, following the procedure below. Immediately after irradiation, a round shovel tip, as specified in JIS A 8902, was applied perpendicularly to the tube axis of the test specimen at the impact test site (infrared irradiation site). A 10kg weight, with a cushioning material (CR rubber: 10mm thick, hardness 35) attached to its underside, was dropped onto the shovel from a height of 13cm. The presence or absence of penetration (hole formation) in the test specimen was then observed. The results are shown in Table 1.

[0068] (Example 4, Comparative Example 2) A rigid polyvinyl chloride resin composition was obtained in the same manner as in Example 1, according to the formulation shown in Table 1. Next, a power communication tube was fabricated in the same manner as in Example 1, except that the tube thickness was set to 3.1 mm. The above measurements and tests were performed on the obtained power communication tubes.

[0069] [Table 1]

[0070] The power communication tubes of Examples 1 to 4 exhibited suppressed temperature rise during infrared irradiation and superior compressive strength and impact resistance during infrared irradiation. [Explanation of Symbols]

[0071] 1. Power and telecommunications pipe 2 Straight pipe section 3. Receptacle 4 Tapered pipe section 5 Insertion part 6 Insertion markings 11 rubber rings 21. Body 110 Power Cable 120 Power conduit 130 Power tube 210 Communication Cable 220 Communication conduits 230 communication tubes 240 sheath pipes

Claims

1. A method for manufacturing a cable protection tube having a receiving end at the end of a straight pipe section, A process of forming cylindrical tubes of the same diameter by extruding a gray, rigid vinyl chloride resin composition containing vinyl chloride resin and pigment using an extruder, The process includes a step of expanding the diameter of the end of the aforementioned pipe, The aforementioned pigment consists of a mixture of non-carbon inorganic pigments and organic pigments. A method for manufacturing a cable protection tube, wherein the organic pigment is a blue organic pigment.

2. A method for manufacturing a cable protection tube having a receiving end at the end of a straight pipe section, A process of forming cylindrical tubes of the same diameter by extruding a gray, rigid vinyl chloride resin composition containing vinyl chloride resin and pigment using an extruder, The process includes a step of expanding the diameter of the end of the aforementioned pipe, The aforementioned pigment consists solely of non-carbon inorganic pigments. The non-carbon inorganic pigment consists of a mixture of a colored non-carbon inorganic pigment and a white non-carbon inorganic pigment. A method for manufacturing a cable protection tube, wherein the colored non-carbon inorganic pigment consists of a mixture of a composite oxide of chromium oxide and iron oxide and a blue inorganic pigment.

3. The method for manufacturing a cable protection tube according to claim 1 or 2, wherein the step of expanding the diameter of the end of the tube is to immerse the end of the tube in a heated oil bath to heat it, and then insert the heated end of the tube into an expansion mold to expand its diameter.

4. The cable protection tube includes a tapered section that connects the straight section and the receiving section. The method for manufacturing a cable protection tube according to any one of claims 1 to 3, wherein the receiving portion is provided with an enlarged diameter portion on the inner circumferential surface of the receiving portion for accommodating a rubber ring.

5. The method for manufacturing a cable protection tube according to any one of claims 1 to 4, wherein the step of forming the tube is to form the tube such that the value obtained by dividing the outer diameter of the tube by the thickness of the tube is 15 to 17.

6. The method for manufacturing a cable protection tube according to any one of claims 1 to 4, wherein the step of forming the tube is to form the tube such that the value obtained by dividing the outer diameter of the tube by the thickness of the tube is 17 to 20.

7. The method for manufacturing a cable protection tube according to any one of claims 1 to 4, wherein the step of forming the tube is to form the tube such that the value obtained by dividing the outer diameter of the tube by the thickness of the tube is between 30 and 38.

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